Self-organizing control system

ABSTRACT

This disclosure relates to improvements in self-organizing control logic configurations having particular application to automatically or remotely piloted vehicles. The improvements include the use of multiple-point (time-distributed) functions for control system performance assessment, the use of performance assessment value-signal magnitude information to govern parameter step sizes, and means for controlling an object that is rotating with a determinable angular rate but unknown phase angle relative to a fiducial angular position of the object.

United States Patent [191 Barron et a1. 1

1 SELF-ORGANIZING- CONTROL SYSTEM Inventors: Roger L. Barron; DixonCleveland, both of Annandale, Va.

Adaptronics, Inc., McLean, Va.

Jan. 31, 1972 Appl. No.: 222,072

[73] Assignee:

[22] Filed:

[52] US. Cl... 244/3.15, 340/1725, 235/.150.l API;

235/150 OPT, 244/77 M [51] Int. Cl. F41q 7/00 [58] Field of Search244/315, 77 M, 3.23; 340/1725; 235/150.l API, 150 OPT References Cited v1 UNITED STATES PATENTS 3,411,736 11/1968 Kelly ..244/3.l5

[111 3,794,271 1 Feb. 26, 1974 12/1968 Martin et a1. 244/3.15 4/1969 DoMau Lam 244/3.15

Primary Examiner-Samuel Feinberg [5 7] ABSTRACT This disclosure relatesto improvements in selforganizing control logic configurations havingparticular application to automatically or remotely piloted vehicles.The improvements include the use of multiple-point (time-distributed)functions for control sys tem performance assessment, the use ofperformance assessment value-signal magnitude information to governparameter step sizes, and means for controlling an object that isrotating with a determinable angular rate but unknown phase anglerelative to a fiducial angular position of the object.

15 Claims, 6 Drawing Figures COMPUTE E COMPYUTE Vn COMPUTE 0?, COMPUTE is c (FIGURE 2) (FlGURES 5,6)

COMPUTE (FIGURES 5,6)

( ENTER COMPUTE lv l SET |og|= lv lv i 1 main EXIT COMPUTE mogl COMPUTEA01; v

COM PUTE mmg w PAIENIEDFEBZS I974 SHEEI 6 BF 6 mmtij 15417532 mwtij wOu.

1 SELF-ORGANIZING CONTROL SYSTEM improvements include: (a) the use ofmultiple-point (time-distributed) functions for control systemperformance assessments, (b) the use of performance assessmentvalue-signal magnitudeinformation to govern parameter step sizes, andmeans for controlling an object that is rotating with a determinableangular rate but unknown phase angle relative to a fiducial angularposition of the object, said means incorporating first means forcomputing the performance of the SOC in accordance with variations ofcontrol system response as appearing in a system error signal, secondmeans for estimating the phase angle of the object in accordance with acorrelation between changes in the system performance computed by saidfirst means with changes in the estimated phase angle, and third meansfor generating signals that actuate the controlled object in accordancewith said'estimated phase angle from said second means. These and otherconcepts are discussed below.

The published literature on self-organizing control describes SOCtechniques that use single point determinations of v, the performanceassessment (PA) value signal, and considers only the polarity of thissignal. This invention relates to theuse of multi-point performanceassessment (PA) algorithms and establishes the parameter step sizes byusing value-signal magnitude information. These logic conceptions have agreat deal of utility for aerospace applications, as well as forcontrols in industry, for the following reasons:

a. The sampling rate of the SOC can be significantly .reduced, withconsequent easing of bandwidth requirements on electroniccircuits.

b. Tolerance to sensor-noise is improved and requirements for sensorresolution are relaxed.

c. The $00 adapts to much widerranges of gains and frequencies of thecontrolled objects.

In addition, techniques have been devised that operate in conjunctionwith the other logic refinements mentioned above to reduce steady-statehunting exhib ited by the SOC to a'negligible amplitude in thoseapplications not involving large transport delays.

In the published literature, the correlation process used by the SOC isthat expressed by the equation I P IIAPI (sgn v) (sgn Au) where: I

Ap increment to probability, p, that the next Au 0 I v lApl constant(non-zero if p p p zero if p pmin or pma1) sgn v polarity of valuesignal, -v sgn Au polarity of last increment to control signal,

u The value signal polarity has been computed from the relationship 8" v8" PX g" in which e, e T is the predicted (extrapolated) control systemerror, where e is the instantaneous control system error. To compute sgne it has been necessary to determine the third derivative of thecontrolledobject response, and this has imposed rather stringent demandson system hardware.

More generally, one has Ap K V Auin which K positive constant T1multi-point value signal A17 multi-point experiment history Multi-PointValue Signal Although no real system can compute a derivative in zerotime (i.e., by using true infinitesimals of displacement and time),prior SOC practice has been to employ high-bandwidth sensors andelectronic circuitry so that the limiting case of a pure derivative isapproached quite closely in terms of the natural time constants of thephysical system. Unfortunately, formany applications the bandwidthrequirements imposed by system performance specifications are notreadily satisfied by available hardware, particularly that suitable forlowcost systems. 7

In accordance with this invention, there are provided techniques wherebya multi-point value signal, V, can be computed and used in the SOC. Themulti-point value signal, as its name suggests, is one that iscalculated from a number of time-distributed samples of the systemresponse variable(s). The fundamental idea in this technique is tocompute an estimate, I 1 of a variable indicative of the control systemresponse which would have existed at time t, had the system continued onthe path it was following prior to the most recent control actions. Thenumerical difference between this estimate and the actual systemresponse at time t,,, denoted E,,, that is measured is therebyindicative of whether these recent actions improved or worsened thebehavior of the system. Thus, symbolically V= E, E,

where (for thepresent discussion only) it is assumed that E and E areboth always non-negative functions of time.

One embodiment is a quadratic formula for calculation of E n n-1 n-2rr-3 whence number, k, of past points, each point separated from itsimmediate neighbors by time intervals At.

Multi-Point Experiment History The SOC correlation logic separatescausal from extraneous trend information by integrating a plurality ofAps. Thus, random environmental factors are ignored, on the average,whereas the significant response characteristics of the plant areidentified. In correlations performed with a multi-point performancevalue signal, it is important to compute a measure of recent controlactions that is properly indicative of the pattern of these actions.Obviously, the earlier the action, within limits, the greater itsinfluence on both T5,, and E The last action taken, that is, the mostimmediate prior Au, has the least over-all influence on 1 1,, and E,,,but it may be the most important action taken in terms of the numericaldifference between E,, and E Accordingly, a weighted sum of the recentAus is utilized, viz.

The non-negative weights; w w w may be selected in accordance with theharmonic sequence (such that w l, w one-half, w l/k.

Automatic Adjustment of SOC Experiment Step Sizes Use of fixed values of|Au| the SOC experiment step size, has, in the past, limited the rangesof controlledobject gains and frequencies over which a given SOC couldfunction. The dynamic range of differentiation circuits also has been aseverely limiting factor, but this latter problem is largely overcome bythe multipoint techniques just outlined. In accordance with the presentinvention, automatic adjustment of Au is provided by reference to themagnitude of V.

The following algorithm is used:

Step 1. Compute li7,,|.

Step 2. If IV I li l set lAu,,I =f lAu,, where [Au,.|= j Au l V 7 7* Inthis Way, the magnitude of the parameter is increased (geometric growthrate) until the minimum acceptable IVI is achieved. This insuresobservability in the controls sense. Likewise, the parameter magnitudeis decreased (geometric decay rate) if necessary to avoid excessivelylarge This keeps the disturbances introduced by the SOC experiments frombeing larger than necessary.

l nl s WII use 4 Estimating Unknown Phase'Angle of Controlled RotatingObject and Generating Actuation Signals in Accordance Therewith In manycontrol system applications, a controlled object is rotating at a knownor measurable rate but with an unknown phase angle about a given bodyaxis, here denoted the x or roll axis, and control of pitch and yawmotions is to be established by producing torques about orthogonal axes,y and z, respectively, which are fixed in the body perpendicular to thex axis and therefore rotate with the body. Automatically or remotelycontrolled flight vehicles may fit within this category. More generally,any system or process having an unknown phase angle that is to beidentified via a self-organizing control method is amenable to thefollowing approach.

A Ring Counter is implemented, such that its content, d is indicative atany instant, t,,, of the current best estimate of the unknown phaseangle parameter. This output signal is transferred to a summing devicehaving as its other input the time integral of the known or measurablevalue of the angular rate (e.g., the roll rate) of the system. Theoutput of this summing device constitutes the instantaneous estimate ofthe angular position (e.g., roll attitude) of the system, and thisangular position estimate is transferred to sine and cosine computingelements to obtain time-varying waveforms having suitable actuationproperties, as discussed further herein below. The input to the RingCounter is an increment, Ad generated by self-organizing control logic,as discussed in detail herein below.

Other Factors Nearly quiescent steady-state operation of the SOC isachieved by use of a variable gain, G(E, E), on the u signal, followedby an augmented integrator of the form (in LaPlace transform notation) 1l/T s. A representative relationship for the variable gain is G. IE. (TEm] +6..."

where G z 0. The integrator causes the system to migrate to the level atwhich G 0, thus producing the requisite steady-state force (or torque)without signficant variations in output Objects It is therefore anobject of the invention to provide a method and means for supplying amulti-point value signal in a self-organizing control system.

It is a further object of this invention to provide a method and meansfor supplying a multi-point experiment history in SOC correlation logic.

It is a yet further object of this invention to provide a method andmeans for automatic adjustment of step size of experiments conducted byan SOC.

It is a yet further object of this invention to provide a method andmeans for estimating the unknown phase angle of a rotating object andgenerating a control signal in accordance therewith.

The above objects and still further objects of the invention willimmediately become apparent to those skilled in the art afterconsideration of the following FIGURES 4 FIG. I is a block diagram of aself-organizing controller in accordance with the present invention;

' FIG. 2 is a diagram of the interrelation among FIGS. 3 to 5, alsoshowing the use of a Ring Counter, the content of which is the estimatedphase angle of a controlled rotating object;

FIG. 3 is the SOC Correlation Logic for determination of the polarity ofexperimental changes in the estimated phase angle of a controlledrotating object;

FIG. 4 is a flow chart showing a method for computation of the SOCexperiment step sizes used in estimating the phase angle of thecontrolled rotating object.

FIG. 5 is a flow chart of a method for generating sinusoidally-varyingand cosinusoidally-varying signals having a phase angle estimated inaccordance with the invention and frequency and amplitude determined inaccordance with the present invention.

FIG. 6 is a functional block diagram of circuitry for performing themethod of FIG. 5.

DISCUSSION Referringnow to FIG. 1, the first block implements thecomputation of E,,, a variable indicative of the control systemresponse.'ln the application of the improve-- ments discussed herein tothe control of a rolling vehicle that is guided by reference toline-of-sight (LOS) angular rate components, h and A relative torotating body pitch and yaw aites, respectively, a'preferred embodimentof the function E,, is given by thefollowing relationship I Y E,, 0,, Ria i i... ts'gmfirr wherein A: is the timei'ni'?val between 1355553753P* is the known or measured roll rate. It is seen that Equation 10provides positive semi-definite form for the quantity E,,. The method ofPA discussed herein below requires such a form, but it is not necessarythat the specific function of Equation 10 be implemented, and otherembodiments will be apparent to those skilled in the art. The essentialconsideration is that of two time histories of E,,, that which decreasesor increases more slowly is the preferred time history, the object ofthe improved self-organizing control system being (in this instance) tochange E,- toward zero, if I possible, and in any event, to slow therate of increase in I5, so that this variable has a smaller magnitude inthe presence of the control actionsv by the SOC than it would have hadotherwise.

The second block in FIG. 1 implements the PA logic in accordance with arelationship of the form l=k i i (11) for which a special embodiment isvi" E 3 3E 2 E The third block within FIG. 1 realizes.the computation inaccordance with the present invention, and the logic of this computationis shown in detail in FIGS. 2, 3, and 4.

FIG. 2 illustrates the use of the Ring Counter in acas shown in FIG. 4.Both these logic elements receive the value signal input v, obtained inaccordance with the PA method and means discussed herein above. The

Ring Counter has as its content a coded value of the es timated phaseangle, and decoder logic is used to obtain this phase angle. Inaccordance with the present invention, the phase angle is taken to beproportional to the content of the Ring Counter; i.e., as a binary bitmoves around an otherwise empty counter, this bit signifies by itsposition in the counter the instantaneous estimate of the phase angle.As shown in FIG. 2, Step Size Override Logic is used to increase theincrement magnitude within the Ring Counter if a sequence of eight ormore unsuccessful estimates have been made. .1. thi 992555 eavns s sefestim e is .1 be one in which sgn v,, 1. Furthermore, the size of stepcalled for by the Step Size Override Logic can be made to depend uponthe number of unsuccessful experiments conducted in an uninterruptedsuccession of such experiments. The logic for a preferred embodiment andof said override means is shown in FIG. 2.

FIG. 3, illustrating the SOC Correlation Logic, diagrams a novel meansfor implementation of a weighted sum of prior step polarities employedbythe Correlation Logic. The specific numerical weights shown are thoseof a preferred but not necessary embodiment. The weights are applied tobinary output of a tapped shift register, and the weighted sum ismultiplied by sgn v,, to obtain the probability bias signal, x,,, thatis, in turn used in the way disclosed by Roger L. Barron in US. Pat. No.3,460,096 (Self-Organizing Control System).

FIG. 4 is a logic flow chart presented in accordance with the presentinvention to diagram a novel method for selection of SOC experiment stepsizes as a function of v,,. As is seen from this diagram, if themagnitude v,, is less than a threshold value l minl the step size isincreased up to a predetermined limit in accordance with a geometricgrowth procedure. Conversely, if the magnitude of v, is greater than athreshold lv l, the step size is decreased to a predetermined lowerlimit in accordance with a geometric decay law. In FIG. 4, f is greaterthan unity, f is less than unity so as to realize geometric growth anddecay histories.

FIGS. 5 and 6 diagrams a method and means for computing vehicle actuatorcommands S and S relative to body-mounted (i.e., roll) pitch and yawactuators, respectively. It is readily seen from these figuresmagnitudes of the cosinusoidal and sinusoidal excitation signals aredetermined in accordance with the following function of E,

limiters (see FIG. 6) are useful for cases of small P* as a means foreliminating any steady-state following errors. v

APPENDIX The following is a program for simulating the controller of thepresent invention and the dynamics of a controlled plant as run on anEAl-6 4O computer:

REAL LDHeLDDMnLDALDD:LDBaKTskEoKi:KPCV

L5G CAL SENSE CQMMGN IINPUT/ D1: P51 :P: Cu F5; Fl PHIMIN: C00 Cl sKPCVoRBASEO 0 WN VMX DELCMN: DCPMX: DQDNX: DRDMX DQMX DLMXvPHO; OM61 CM 620Va 9 RflPHZMGODKKQEOIBQBBiBQJKEKTJ a K: NENaNPFxNT CALL TYP1N DT2 32:103) DTS DT SIGM DYE oS DT E? (SENSW(8)) G3 LDE 0o LDN a Do INIT O ED onDRD 0. DRD D RBQSE m BBASEO PHK m 0 PH 53 on EU E1 0e W8 on PHIMAG B O.PHISGN 0o DRCP m 00 DVD 0:

DVDD 8 0 GDDD a Do Kobe m 00 IF (MGlKKNTHfiIM'P-NT)0NE00) GS TC; 1B0

TaEIaGJPHIJAoPHaLD D0 GD. DFLC: DU VNJFIIIMAGD PHI SEN they-NJ PNI BQCPDDBCPDQC) DEC) DQD DBD: DU:

0 DVD: DVDD GDD: GDDD: LDB: LDM LDDM W) m l.

KNIT 1 H05 RX El RBASE C=KEEP PAST E UALUESa WEN D6 10 I laNEN J WEN-1+1ENK J+D ENKhJ) MK) 31 EN C--CGMPUTE VN UN ENKKA) 3e#(ENK(2)-ENK(3)) 3&5120 T6 TO PHIMAX CO*PHIMIN C1*EN IF(PHIMAGGT@|PHIMAX) PHIMAG PHIMAXC--CGMPUTE PHI SIGN 130 KN %(3) 8 8(2) @(2) W(l) PM W FN KN IF(ABS(PN)GT-PMAX) PHISGQ 9(1) 8 PHISGN CCOMPUTE PHI PHI 8 PHIPHISGN*PHIMAG RBRAS E RX RETURN QED Though the invention has beendescribed with respect to a specific embodiment thereof, many variationsand modifications will immediately become apparent to those skilled inthe art. It is therefore the intention that the appended claims beinterpreted as broadly as possible in view of the prior art to includeall such variations and modifications.

We claim:

1. In a self-organizing control system for controlling a controllableobject which is rotating at a determinable angular rate and unknownphase angle relative to a fiducial angular position of said object,

a. first means responsive to variations of control system response forproviding an error signal which is computed from said variations ofcontrol system response,

b. second means responsive to said error signal and changes in theestimated phase angle of said object for estimating the phase angle ofsaid object, and

c. third means responsive to said estimated phase angle to provideactuation signals to control said controllable object.

2. A self-organizing control system as set forth in claim 1 wherein saidfirst means includes fourth means to compute said error signal bysampling a plurality of time-distributed samples of the response of saidcontrol system, said fourth means incorporating the sum of numericallyweighted values of said samples taken at finite time intervals.

3. A self-organizing control system as set forth in claim 1 wherein saidsecond means includes fifth means for incorporating the product of afunction of said error signals and the sum of numerically weightedvalues of samples of said estimated phase angle taken at finite timeintervals.

4. A self-organizing control system as set forth in claim 2 wherein saidsecond means includes fifth means for incorporating the product of afunction of said error signals and the sum of numerically wieghtedvalues of samples of said estimated phase angle taken at finite timeintervals.

5. A self-organizing control system as set forth in claim 1 wherein saidsecond means includes means for incorporating the product of a functionof changes in said estimated phase angle and a function of said errorsignal.

6. A self-organizing control system as set forth in claim 2 wherein saidsecond means includes means for incorporating the product of a functionof changes in said estimated phase angle and a function of said errorsignal.

7. A self-organizing control system as set forth in claim 3 wherein saidfifth means includes a ring counter and sixth means for computing theestimated phase angle as a function of the contents of said ringcounter.

8. A self-organizing control system as set forth in claim 4 wherein saidfifth means includes a ring counter and sixth means for computing theestimated phase angle as a function of the contents of said ringcounter.

9. A self-organizing control system as set forth in claim wherein saidsecond means includes means for computing the numerical differencebetween said error signal and established thresholds.

10. A self-organizing control system as set forth in claim 6 whereinsaid second means includes means for computing the numerical differencebetween said error signal and established thresholds.

11. A self-organizing control system as set forth in claim 9 whereinsaid third means includes means to compute large changes in saidestimated value of an unknown parameter under conditions of saidnumerical difference being small and small changes in said estimatedvalue under conditions of said numerical differences being large.

12. A self-organizing control system as set forth in claim 10 whereinsaid third means includes means to compute large changes in saidestimated value of an unknown parameter under conditions of saidnumerical difference being small and small changes in said estimatedvalue under conditions of said numerical differences being large.

13. A self-organizing control system as set forth in claim 1 furtherincluding seventh means including sinusoidal and cosinusoidal wavegenerators to actuate said controlled object.

14. A self-organizing control system as set forth in claim 13 includingeighth means including means for computing a function of the amplitudesof said waves.

15. A self-organizing control system as set forth in claim 1 furtherincluding eighth means including limit means for limiting the magnitudeof said actuation signals.

1. In a self-organizing control system for controlling a controllableobject which is rotating at a determinable angular rate and unknownphase angle relative to a fiducial angular position of said object, a.first means responsive to variations of control system response forproviding an error signal which is computed from said variations ofcontrol system response, b. second means responsive to said error signaland changes in the estimated phase angle of said object for estimatingthe phase angle of said object, and c. third means responsive to saidestimated phase angle to provide actuation signals to control saidcontrollable object.
 2. A self-organizing control system as set forth inclaim 1 wherein said first means includes fourth means to compute saiderror signal by sampling a plurality of time-distributed samples of theresponse of said control system, said fourth means incorporating the sumof numerically weighted values of said samples taken at finite timeintervals.
 3. A self-organizing control system as set forth in claim 1wherein said second means includes fifth means for incorporating theproduct of a function of said error signals and the sum of numericallyweighted values of samples of said estimated phase angle taken at finitetime intervals.
 4. A self-organizing control system as set forth inclaim 2 wherein said second means includes fifth means for incorporatingthe product of a function of said error signals and the sum ofnumerically wieghted values of samples of said estimated phase angletaken at finite time intervals.
 5. A self-organizing control system asset forth in claim 1 wherein said second means includes means forincorporating the product of a function of changes in said estimatedphase angle and a function of said error signal.
 6. A self-organizingcontrol system as set forth in claim 2 wherein said second meansincludes means for incorporating the product of a function of changes insaid estimated phase angle and a function of said error signal.
 7. Aself-organizing control system as set forth in claim 3 wherein saidfifth means includes a ring counter and sixth means for computing theestimated phase angle as a function of the contents of Said ringcounter.
 8. A self-organizing control system as set forth in claim 4wherein said fifth means includes a ring counter and sixth means forcomputing the estimated phase angle as a function of the contents ofsaid ring counter.
 9. A self-organizing control system as set forth inclaim 5 wherein said second means includes means for computing thenumerical difference between said error signal and establishedthresholds.
 10. A self-organizing control system as set forth in claim 6wherein said second means includes means for computing the numericaldifference between said error signal and established thresholds.
 11. Aself-organizing control system as set forth in claim 9 wherein saidthird means includes means to compute large changes in said estimatedvalue of an unknown parameter under conditions of said numericaldifference being small and small changes in said estimated value underconditions of said numerical differences being large.
 12. Aself-organizing control system as set forth in claim 10 wherein saidthird means includes means to compute large changes in said estimatedvalue of an unknown parameter under conditions of said numericaldifference being small and small changes in said estimated value underconditions of said numerical differences being large.
 13. Aself-organizing control system as set forth in claim 1 further includingseventh means including sinusoidal and cosinusoidal wave generators toactuate said controlled object.
 14. A self-organizing control system asset forth in claim 13 including eighth means including means forcomputing a function of the amplitudes of said waves.
 15. Aself-organizing control system as set forth in claim 1 further includingeighth means including limit means for limiting the magnitude of saidactuation signals.